Download Chapter 18: Properties of Atoms and the Periodic Table

18
Properties of Atoms
and the Periodic Table
I
t might surprise you to know that
these clouds of Jupiter, your pencil or pen, and you have something in common. Much of the
universe is made up of particles so
small they cannot even be seen, called
atoms. But there are particles even
smaller than atoms. What are these
tiny pieces of the universe? In this
chapter you will learn about atoms
and their components—protons,
neutrons, and electrons.
What do you think?
Science Journal Look at the picture
below with a classmate. Discuss what
you think this might be. Here’s a
hint: It’s a winning combination you
couldn’t live without. Write your
answer or your best guess in your
Science Journal.
542
ow do detectives solve a crime when no witnesses saw it happen? How do scientists study
atoms when they cannot see them? In situations such
as these, techniques must be developed to find clues
to answer the question. Do the activity below to see
how clues might be gathered.
EXPLORE H
ACTIVITY
Inferring what you can’t observe
1. Take an envelope from your teacher.
2. Place an assortment of dried beans in
the envelope and seal it. WARNING:
Do not eat any lab materials.
3. Trade envelopes with another group.
4. Without opening the envelope, try
to figure out the types and number of
beans that are in the envelope. Record
a hypothesis about the contents of the envelope in your Science Journal.
5. After you record your hypothesis, open the envelope and see what is inside.
Observe
How many of each kind of bean did you find? Was your hypothesis correct?
FOLDABLES
Reading &Study
& Study
Skills
Making a Know-Want-Learn Study Fold Make the following
Foldable to help you identify what you already know and what
you want to know about properties of atoms.
1. Stack two sheets of paper in front of you so the short side of both sheets is at the top.
2. Slide the top sheet up so that about 4 cm of the bottom sheet shows.
3. Fold both sheets top to bottom to form four tabs
and staple along the fold, as shown.
4. Label the top flap Atoms. Then label the other
flaps Know, Want, and Learned as shown. Before
you read the chapter, write what you know
about atoms on the Know tab and what you
want to know on the Want tab.
5. As you read the chapter, list the things you learn
about atoms on the Learned tab.
Atoms
543
SECTION
Structure of the Atom
Scientific Shorthand
■
Identify the names and symbols of
common elements.
■ Identify quarks as subatomic
particles of matter.
■ Describe the electron cloud model
of the atom.
■ Explain how electrons are
arranged in an atom.
Vocabulary
atom
nucleus
electron
proton
neutron
quark
electron cloud
Everything you see, touch, and
breathe is composed of tiny atoms.
Do you have a nickname? Do you use abbreviations for long
words or the names of states? Scientists also do this. In fact, scientists have developed their own shorthand for dealing with
long, complicated names.
Do the letters C, Al, Ne, and Ag mean anything to you? Each
letter or pair of letters is a chemical symbol, which is a short or
abbreviated way to write the name of an element. Chemical
symbols, such as those in Table 1, consist of one capital letter or
a capital letter plus one or two small letters. For some elements,
the symbol is the first letter of the element’s name. For other elements, the symbol is the first letter of the name plus another letter from its name. Some symbols are derived from Latin. For
instance, Argentum is Latin for “silver.” Elements have been
named in a variety of ways. Some elements are named to honor
scientists, for places, or for their properties. Other elements are
named using rules established by an international committee.
Regardless of the origin of the name, scientists derived this
international system for convenience. It is much easier to write
H for hydrogen, O for oxygen, and H2O for dihydrogen oxide
(water). Because scientists worldwide use this system, everyone
understands what the symbols mean.
Table 1 Symbols of Some Elements
Element
Symbol
Aluminum
Al
Calcium
Symbol
Element
Symbol
Gold
Au
Mercury
Hg
Ca
Helium
He
Nitrogen
N
Carbon
C
Hydrogen
H
Oxygen
O
Chlorine
Cl
Iodine
I
Potassium
K
Copper
Cu
Iron
Fe
Silver
Ag
Fluorine
F
Magnesium
Mg
Sodium
Na
544
Element
CHAPTER 18 Properties of Atoms and the Periodic Table
Quarks
Electron
cloud
Neutron
(No charge)
Quarks
Nucleus
Atom
Atomic Components
An element is matter that is composed of one type of atom,
which is the smallest piece of matter that still retains the property
of the element. For example, the element silver is composed of
only silver atoms and the element hydrogen is composed of only
hydrogen atoms. Atoms are composed of particles called protons,
neutrons, and electrons, as shown in Figure 1. Protons and
neutrons are found in a small, positively-charged center of the
atom called the nucleus that is surrounded by a cloud containing electrons. Protons are particles with an electrical charge
of 1⫹. Neutrons are neutral particles that do not have an
electrical charge. Electrons are particles with an electrical charge
of 1⫺. Atoms of different elements differ in the number of
protons they contain.
Proton
(1ⴙ charge)
Figure 1
The nucleus of the atom contains
protons and neutrons that are
composed of quarks. The proton
has a positive charge and the neutron has no charge. A cloud of
negatively charged electrons surrounds the nucleus of the atom.
What are the particles that make up the atom
and where are they located?
Quarks—Even Smaller Particles
Are the protons, electrons, and neutrons that make
up atoms the smallest particles that exist? Scientists hypothesize
that electrons are not composed of smaller particles and
are one of the most basic types of particles. Protons and neutrons, however, are made up of smaller particles called quarks.
So far, scientists have confirmed the existence of six uniquely
different quarks. Scientists theorize that an arrangement of
three quarks held together with the strong nuclear force produces a proton. Another arrangement of three quarks produces
a neutron. The search for the composition of protons and neutrons is an ongoing effort.
Research Visit the
Glencoe Science Web site at
science.glencoe.com for
more information about
ongoing research at the Fermi
National Accelerator Laboratory. Communicate to your
class what you learn.
SECTION 1 Structure of the Atom
545
Figure 2
The Tevatron is a huge
machine.
This aerial photograph of Fermi National Accelerator Laboratory shows the
circular outline of the Tevatron
particle accelerator.
This
close-up photograph of the
Tevatron gives you a better
view of the tunnel. Why is such
a long tunnel needed?
Finding Quarks To study quarks, scientists accelerate
Figure 3
Bubble chambers are used by
scientists to study the tracks
left by subatomic particles.
charged particles to tremendous speeds and then force them to
collide with—or smash into—protons. This collision causes the
proton to break apart. The Fermi National Accelerator Laboratory, a research laboratory in Batavia, Illinois, houses a machine
that can generate the forces that are required to collide protons.
This machine, the Tevatron, shown in Figure 2, is approximately 6.4 km in circumference. Electric and magnetic fields
are used to accelerate, focus and collide the
fast-moving particles.
The particles that result from the collision
are detected in a device called a bubble chamber in which the particles leave tracks. Just as
police investigators can reconstruct traffic
accidents from tire marks and other clues at
the scene, scientists are able to examine and
gather information from the tracks left after
proton collisions, as shown in Figure 3. Studying the tracks reveals information about the
inner structure of the atom. Scientists then use
inference to identify the subatomic particles.
The Sixth Quark Finding evidence for the
existence of the quarks was not an easy task.
Scientists found five quarks and hypothesized
that a sixth quark existed. However, it took a
team of nearly 450 scientists from around the
world several years to find the sixth quark.
The tracks of the sixth quark were hard to
detect because only about one billionth of a
percent of the proton collisions performed
showed the presence of a sixth quark—
typically referred to as the top quark.
546
CHAPTER 18 Properties of Atoms and the Periodic Table
Models—Tools for Scientists
Scientists and engineers use models to represent things that
are difficult to visualize—or picture in your mind. You might
have seen models of buildings, the solar system, or airplanes.
These are scaled-down models. Scaled-down models allow you
to see either something too large to see all at once, or something
that has not been built yet. Scaled-up models are often used to
visualize things that are too small to see. Atoms are very small.
To give you an idea of how small the atom is, it would
take about 24,400 atoms stacked one on top of the other to
equal the thickness of a sheet of aluminum foil. To study the
atom, scientists have developed scaled-up models that they can
use to visualize how the atom is constructed. For the model to
be useful, it must support all of the information that is known
about matter and the behavior of atoms. As more information
about the atom is collected, scientists change their models to
include the new information.
Why do scientists use models?
The Changing Atomic Model You know now that all
matter is composed of atoms, but this was not always known.
Around 400 B.C., Democritus proposed the idea that atoms
make up all substances. However, a famous Greek philosopher,
Aristotle, disputed Democritus’s theory and proposed that matter was uniform throughout and was not composed of smaller
particles. Aristotle’s incorrect theory was accepted for about
2,000 years. In the 1800s, John Dalton, an English scientist, was
able to offer proof that atoms exist.
Dalton’s model of the atom, a solid sphere shown in Figure 4,
was an early model of the atom. As you can see in Figure 5, the
model has changed somewhat over time. As each scientist performed experiments and learned a little bit more about the structure of the atom, the model was modified. The model in use
today is the accumulated knowledge of almost two hundred years.
Modeling an
Aluminum Atom
Procedure
1. Arrange 13 3-cm circles
cut from orange paper
and 14 3-cm circles cut
from blue paper on a
flat surface to represent
the nucleus of an atom.
Each orange circle represents one proton, and
each blue circle represents
one neutron.
2. Position 2 holes punched
from red paper about 20
cm from your nucleus.
3. Position 8 punched holes
about 40 cm from your
nucleus.
4. Position 3 punched holes
about 60 cm from your
nucleus.
Analysis
1. How many protons, neutrons, and electrons does
an aluminum atom have?
2. Explain how your circles
model an aluminum atom.
3. Explain why your model
does not accurately
represent the true size
and distances in an
aluminum atom.
Figure 4
John Dalton’s atomic model was a
simple sphere.
SECTION 1 Structure of the Atom
547
VISUALIZING THE ATOMIC MODEL
Figure 5
T
he ancient Greek philosopher Democritus proposed that
elements consisted of tiny, solid particles that could not be
subdivided (A). He called these particles atomos, meaning
“uncuttable.” This concept of the atom’s structure remained largely
unchallenged until the 1900s, when researchers began to discover
through experiments that atoms were composed of still smaller
particles. In the early 1900s, a number of models for atomic
structure were proposed (B-D). The currently accepted model (E)
evolved from these ideas and the work of many other scientists.
A DEMOCRITUS’S
UNCUTTABLE ATOM
Ball of
positive
charge
Negatively
charged
electron
B THOMSON MODEL, 1904 English physicist Joseph
John Thomson inferred from his experiments that
atoms contained small, negatively charged particles.
He thought these “electrons” (in red) were evenly
embedded throughout a positively charged sphere,
much like chocolate chips in a ball of cookie dough.
Positively
charged
nucleus
“Empty space”
containing electrons
C RUTHERFORD MODEL, 1911 Another British
physicist, Ernest Rutherford, proposed that
almost all the mass of an atom—and all its positive charges—were concentrated in a central
atomic nucleus surrounded by electrons.
Electron
cloud
Nucleus
D BOHR MODEL, 1913 Danish physicist Niels Bohr
hypothesized that electrons traveled in fixed orbits
around the atom’s nucleus. James Chadwick, a student
of Rutherford, concluded that the nucleus contained
positive protons and neutral neutrons.
548
E ELECTRON CLOUD MODEL, CURRENT According
to the currently accepted model of atomic structure, electrons do not follow fixed orbits but tend
to occur more frequently in certain areas around
the nucleus at any given time.
The Electron Cloud Model By 1926,
scientists had developed the electron cloud
model of the atom that is in use today. An
electron cloud is the area around the nucleus
of an atom where its electrons are most likely
Electron
found. The electron cloud is 100,000 times
cloud
larger than the diameter of the nucleus. In
contrast, each electron in the cloud is much
smaller than a single proton.
Because an electron’s mass is small and
the electron is moving so quickly around the
nucleus, it is impossible to describe its exact
Nucleus
location in an atom. Picture the spokes on a
moving bicycle wheel. They are moving so
quickly that you can’t pinpoint any single
spoke. All you see is a blur that contains all
of the spokes somewhere within it. In the
same way, an electron cloud is a blur
containing all of the electrons of the atom somewhere within it.
Figure 6
The electrons are located in an
Figure 6 illustrates what the electron cloud might look like.
electron cloud surrounding the
Scientists have determined that the electron cloud is more
nucleus of the atom.
than just a blur. Each electron travels at an average distance from
the nucleus, depending on its energy. These average distances are
referred to as energy levels. Energy levels are areas of the cloud
where the electrons are more likely to be found.
Section
Assessment
1. Write the chemical symbols for the
elements carbon, aluminum, hydrogen,
oxygen, and sodium.
2. What are the names, charges, and locations of three kinds of particles that make
up an atom?
3. What is the smallest particle of matter?
How were they discovered?
4. Describe the electron cloud model of
the atom.
5. Think Critically Explain how a rotating
electric fan might be used to model the
atom. Explain how the rotating fan is
unlike an atom.
6. Concept Mapping Make a concept map for
the parts of an atom. Include the following
terms: electron cloud, nucleus, electrons,
protons, quarks, and neutrons. Provide the location of each particle in the atom. For more help,
refer to the Science Skill Handbook.
7. Solving One-Step Equations The mass of a
–24
proton is estimated to be 1.6726 ⫻ 10 g and
the mass of an electron is estimated to be
–28
9.1093 ⫻ 10 g. How many times larger is the
mass of a proton compared to the mass of an
electron? For more help, refer to the Math
Skill Handbook.
SECTION 1 Structure of the Atom
549
SECTION
Masses of Atoms
Atomic Mass
■
Compute the atomic mass and
mass number of an atom.
■ Identify isotopes of common
elements.
■ Interpret the average atomic mass
of an element.
Vocabulary
atomic number
mass number
isotope
average atomic mass
Most elements exist in more than
one form. Some are radioactive,
and others are not.
The nucleus contains most of the mass of the atom because
protons and neutrons are far more massive than electrons. The
mass of a proton is about the same as that of a neutron—approximately 1.6726 ⫻ 10⫺24 g, as shown in Table 2. The mass of each is
approximately 1,836 times greater than the mass of the electron.
The electron’s mass is so small that it is considered negligible
when finding the mass of an atom, as shown in Figure 7.
If you were asked to estimate the height of your school building, you probably wouldn’t give an answer in kilometers. The
number would be too cumbersome to use. Considering the scale
of the building, you would more likely give the height in a
smaller unit, meters. When thinking about the small masses of
atoms, scientists found that even grams were not small enough to
use for measurement. Scientists need a unit that results in more
manageable numbers. The unit of measurement used for atomic
particles is the atomic mass unit (amu). The mass of a proton or
a neutron is almost equal to 1 amu. This is not coincidence—the
unit was defined that way. The atomic mass unit is defined as
one-twelfth the mass of a carbon atom containing six protons
and six neutrons. Remember that the mass of the carbon atom
is contained almost entirely in the mass of the protons and neutrons that are located in the nucleus. Therefore, each of the 12
particles in the nucleus must have a mass nearly equal to one.
Where is the majority of the mass of an
atom located?
Figure 7
If you held a textbook and placed
a paper clip on it, you wouldn’t
notice the added mass because
the mass of a paper clip is small
compared to the mass of the
book. In a similar way, the
masses of an atom’s electrons
are negligible compared to an
atom’s mass.
550
Table 2 Comparison of Particles in an Atom
Particle
Mass (g)
Charge
Proton
1.6726 ⫻ 10–24
1⫹
Nucleus
Neutron
1.6749 ⫻ 10–24
0
Nucleus
Electron
9.1093 ⫻ 10–28
1⫺
Cloud surrounding
nucleus
CHAPTER 18 Properties of Atoms and the Periodic Table
Location in Atom
Table 3 Mass Numbers of Some Atoms
Element
Symbol
Atomic
Number
Protons
Neutrons
Mass
Number
Average
Atomic Mass*
Boron
B
5
5
6
11
10.81
Carbon
C
6
6
6
12
12.01
Oxygen
O
8
8
8
16
16.00
Sodium
Na
11
11
12
23
22.99
Copper
Cu
29
29
34
63
63.55
* The atomic mass units are rounded to two decimal places.
Protons Identify the Element You learned earlier that
atoms of different elements are different because they have different numbers of protons. In fact, the number of protons tells
you what type of atom you have and vice versa. For example,
every carbon atom has six protons. Also, all atoms with six protons are carbon atoms. Atoms with eight protons are oxygen
atoms. The number of protons in an atom is equal to a number
called the atomic number. The atomic number of carbon is six.
Therefore, if you are given any one of the following—the name
of the element, the number of protons in the element, or the
atomic number of the element, you can determine the other two.
Which element is an atom with six protons in
the nucleus?
Mass Number The mass number of an atom is the sum of
the number of protons and the number of neutrons in the
nucleus of an atom. Look at Table 3 and see if this is true.
If you know the mass number and the atomic number of an
atom, you can calculate the number of neutrons. The number of
neutrons is equal to the atomic number subtracted from the
mass number.
number of neutrons ⫽ mass number ⫺ atomic number
Atoms of the same element with different numbers of neutrons can have different properties. For example, carbon with a
mass number equal to 12 or carbon-12 is the most common
form of carbon. Carbon-14 is present on Earth in much smaller
quantities. Carbon-14 is radioactive and carbon-12 is not.
How is the mass number calculated?
SECTION 2 Masses of Atoms
551
Isotopes
Living organisms on Earth
contain carbon. Carbon-12
makes up 99 percent of this
carbon. Carbon-13 and
carbon-14 make up the
other one percent. Which
isotopes are archaeologists
most interested in when
they determine the age of
carbon-containing remains?
Explain your answer in
your Science Journal.
Not all the atoms of an element have the same number of
neutrons. Atoms of the same element that have different numbers of neutrons are called isotopes. Suppose you have a sample
of the element boron. Naturally occurring atoms of boron have
mass numbers of 10 or 11. How many neutrons are in a boron
atom? It depends upon the isotope of boron to which you are
referring. Obtain the number of protons in boron from the
periodic table. Then use the formula on the previous page to
calculate the number of neutrons in each boron isotope. You can
determine that boron can have five or six neutrons.
Uranium-238 has 92 protons. How many
neutrons does it have?
Problem-Solving Activity
Radioactive Isotopes Help Tell Time
toms can be used to measure the age of bones or rock
formations that are millions of
years old. The time it takes for
half of the radioactive atoms in
a piece of rock or bone to
change into another element is
called its half-life. Scientists use
the half-lives of radioactive isotopes to measure geologic time.
A
Half-lives of Radioactive Isotopes
Radioactive
Element
Changes to this
Radioactive Element
Half-Life
uranium-238
lead-206
4,460 million years
potassium-40
argon-40, calcium-40
1,260 million years
rubidium-87
strontium-87
48,800 million years
carbon-14
nitrogen-14
5,715 years
Identifying the Problem
The table above lists the half-lives of a sample of radioactive isotopes and into
which elements they change. For example, it would take 5,715 years for half of the
carbon-14 atoms in a rock to change into atoms of nitrogen-14. After another
5,715 years, half of the remaining carbon-14 atoms will change, and so on. You
can use these radioactive clocks to measure different periods of time.
Solving the Problem
1. How many years would it take half of the rubidium-87 atoms in a piece of rock
to change into strontium-87? How many years would it take for 75% of the
atoms to change?
2. After a long period, only 25% of the atoms in a rock remained uranium-238.
How many years old would you predict the rock to be? The other 75% of the
atoms are now which radioactive element?
552
CHAPTER 18 Properties of Atoms and the Periodic Table
Identifying Isotopes Models of
Boron-10
Boron-11
two isotopes of boron are shown in
5 Electrons
Figure 8. Because the numbers of
neutrons in the isotopes are different, the mass numbers are also dif5 Electrons
ferent. You use the name of the
element followed by the mass number of the isotope to identify each
isotope: boron-10 and boron-11.
5 Protons
Because most elements have more
ⴙ ⴙ
5 Neutrons
ⴙ
ⴙ
than one isotope, each element has
ⴙ
ⴙ
ⴙ
an average atomic mass. The averⴙ
5 Protons
ⴙ
ⴙ
age atomic mass of an element is
6 Neutrons
the weighted-average mass of the
Nucleus
Nucleus
mixture of its isotopes. For example,
four out of five atoms of boron are boron-11, and one out of five
Figure 8
Boron-10 and boron-11
is boron-10. To find the weighted-average or the average atomic
are two isotopes of boron.
mass of boron, you would solve the following equation:
These two isotopes differ
by one neutron.
4
1
ᎏᎏ(11 amu) ⫹ ᎏᎏ(10 amu) ⫽ 10.8 amu
5
5
The average atomic mass of the element boron is 10.8 amu.
Note that the average atomic mass of boron is close to the mass
of its most abundant isotope, boron-11.
Section
Assessment
1. A chlorine atom has 17 protons and 18 neutrons. What is its mass number? What is its
atomic number?
2. How are the isotopes of an element alike
and how are they different?
3. Why is the atomic mass of an element an
average mass?
4. How would you calculate the number of
neutrons in potassium-40?
5. Think Critically Chlorine has an
average atomic mass of 35.45 amu. The
two naturally occurring isotopes of chlorine
are chlorine-35 and chlorine-37. Why does
this indicate that most chlorine atoms contain 18 neutrons?
6. Comparing and Contrasting How does the
average atomic mass relate to the mass number
of an atom? Use carbon as an example in your
explanation. For more help, refer to the Science Skill Handbook.
7. Using an Electronic Spreadsheet Use a
spreadsheet to construct a table organizing
information about the atomic numbers; atomic
mass numbers; and the number of protons,
neutrons, and electrons in atoms of oxygen-16,
oxygen-17, carbon-12, carbon-14, chlorine-35,
and chlorine-36. Record your calculations in your
Science Journal. For more help, refer to the
Technology Skill Handbook.
SECTION 2 Masses of Atoms
553
SECTION
The Periodic Table
Organizing the Elements
■
Explain the composition of the
periodic table.
■ Use the periodic table to obtain
information.
■ Explain what the terms metal,
nonmetal, and metalloid mean.
Vocabulary
periodic table
group
electron dot diagram
period
The periodic table is an organized
list of the elements that compose all
living and nonliving things that are
known to exist in the universe.
On a clear evening, you can see one of the various phases of
the Moon. Each month, the Moon seems to grow larger, then
smaller, in a repeating pattern. This type of change is periodic.
Periodic means “repeated in a pattern.” Look at a calendar. The
days of the week are periodic because they repeat themselves
every seven days. Months repeat every 12 months. The calendar
is a periodic table of days and months. Calendars are used to
organize your schedule into a convenient format.
In the late 1800s, Dmitri Mendeleev, a Russian chemist,
searched for a way to organize the elements. When he arranged all
the elements known at that time in order of increasing atomic
masses, he discovered a pattern. Figure 9 shows Mendeleev’s early
periodic chart. Chemical properties found in lighter elements
could be shown to repeat in heavier elements. Because the pattern
repeated, it was considered to be periodic. Today, this arrangement is called a periodic table of elements. In the periodic table,
the elements are arranged by increasing atomic number and by
changes in physical and chemical properties.
Figure 9
Mendeleev discovered that the
elements had a periodic pattern
in their chemical properties.
Notice the question marks in
his chart. These were elements
that had not been discovered
at that time.
554
CHAPTER 18 Properties of Atoms and the Periodic Table
Table 4 Mendeleev’s Predictions
Predicted Properties
of Ekasilicon (Es)
Actual Properties
of Germanium (Ge)
Predicted Properties
Actual Properties
Atomic mass ⫽ 72
Atomic mass ⫽ 72.61
High melting point
Melting point ⫽ 938°C
Density ⫽ 5.5 g/cm3
Density ⫽ 5.323 g/cm3
Dark gray metal
Gray metal
Density of EsO2 ⫽ 4.7 g/cm3
Density of GeO2 ⫽ 4.23 g/cm3
Mendeleev’s Predictions Mendeleev had to leave blank
spaces in his periodic table to keep the elements properly lined
up according to their chemical properties. He looked at the
properties and atomic masses of the elements surrounding these
blank spaces. From this information, he was able to predict the
properties and the mass numbers of new elements that had not
yet been discovered. Table 4 shows Mendeleev’s predicted properties for germanium, which he called ekasilicon. His predictions proved to be accurate. Scientists later discovered these
missing elements and found that their properties were
extremely close to what Mendeleev had predicted.
How did Mendeleev organize his periodic chart?
Improving the Periodic Table Although Mendeleev’s
arrangement of elements was successful, it did need some
changes. On Mendeleev’s table, the atomic mass gradually
increased from left to right. If you look at the modern periodic
table, shown in Table 5, you will see several examples, such as
cobalt and nickel, where the mass decreases from left to right.
You also might notice that the atomic number always increases
from left to right. In 1913, the work of Henry G.J. Moseley, a
young English scientist, led to the arrangement of elements
based on their increasing atomic numbers instead of an arrangement based on atomic masses. This new arrangement seemed to
correct the problems that had occurred in the old table. The current periodic table uses Moseley’s arrangement of the elements.
Organizing a Personal
Periodic Table
Procedure
1. Collect as many of the following items as you can
find: feather, penny, container of water, pencil,
dime, strand of hair, container of milk, container
of orange juice, square of
cotton cloth, nickel,
crayon, quarter, container
of soda, golf ball, sheet of
paper, baseball, marble,
leaf, and paper clip.
2. Organize these items into
several columns based on
their similarities to create
your own periodic table.
Analysis
1. Explain the system you used
to group your items.
2. Were there any items on the
list that did not fit into any
of your columns?
3. Infer how your activity
modeled Mendeleev’s work
in developing the Periodic
Table of the Elements.
How is the modern periodic table arranged?
SECTION 3 The Periodic Table
555
PERIODIC TABLE OF THE ELEMENTS
1A
1
1
Hydrogen
1
Atomic number
1
Symbol
H
2A
2
H
Lithium
3
2
3
4
5
6
7
Liquid
State of
matter
Solid
Synthetic
1.008
Atomic mass
1.008
Gas
Hydrogen
Element
Beryllium
4
Li
Be
6.941
9.012
Sodium
11
Magnesium
12
Na
Mg
22.990
24.305
Potassium
19
Calcium
20
3B
3
Scandium
21
4B
4
Titanium
22
5B
5
Vanadium
23
6B
6
Chromium
24
7B
7
Manganese
25
8B
8
Iron
26
9
Cobalt
27
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
39.098
40.078
44.956
47.867
50.942
51.996
54.938
55.845
58.933
Rubidium
37
Strontium
38
Yttrium
39
Zirconium
40
Niobium
41
Molybdenum
42
Technetium
43
Ruthenium
44
Rhodium
45
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
85.468
87.62
88.906
91.224
92.906
95.94
(98)
101.07
102.906
Cesium
55
Barium
56
Lanthanum
57
Hafnium
72
Tantalum
73
Tungsten
74
Rhenium
75
Osmium
76
Iridium
77
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
132.905
137.327
138.906
178.49
180.948
183.84
186.207
190.23
192.217
Francium
87
Radium
88
Actinium
89
Rutherfordium
104
Dubnium
105
Seaborgium
106
Bohrium
107
Hassium
108
Meitnerium
109
Fr
Ra
Ac
Rf
Db
Sg
Bh
Hs
Mt
(223)
(226)
(227)
(261)
(262)
(266)
(264)
(277)
(268)
The number in parentheses is the mass number of the longest lived isotope for that element.
Lanthanide series
Actinide series
556
Cerium
58
Praseodymium
59
Neodymium
60
Promethium
61
Samarium
62
Europium
63
Ce
Pr
Nd
Pm
Sm
Eu
140.116
140.908
144.24
(145)
150.36
151.964
Thorium
90
Protactinium
91
Uranium
92
Neptunium
93
Plutonium
94
Americium
95
Th
Pa
U
Np
Pu
Am
232.038
231.036
238.029
(237)
(244)
(243)
CHAPTER 18 Properties of Atoms and the Periodic Table
Metal
8A
18
Metalloid
Nonmetal
3A
13
Recently
discovered
4A
14
10
2B
12
Copper
29
Nickel
28
6A
16
Helium
2
7A
17
He
4.003
Boron
5
1B
11
5A
15
Zinc
30
Carbon
6
Nitrogen
7
Oxygen
8
Neon
10
Fluorine
9
B
C
N
O
F
Ne
10.811
12.011
14.007
15.999
18.998
20.180
Aluminum
13
Silicon
14
Phosphorus
15
Sulfur
16
Chlorine
17
Argon
18
Al
Si
P
S
Cl
Ar
26.982
28.086
30.974
32.065
35.453
39.948
Gallium
31
Germanium
32
Arsenic
33
Selenium
34
Bromine
35
Krypton
36
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
58.693
63.546
65.39
69.723
72.64
74.922
78.96
79.904
83.80
Palladium
46
Silver
47
Cadmium
48
Indium
49
Tin
50
Antimony
51
Tellurium
52
Iodine
53
Xenon
54
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
106.42
107.868
112.411
114.818
118.710
121.760
127.60
126.904
131.293
Platinum
78
Gold
79
Mercury
80
Thallium
81
Lead
82
Bismuth
83
Polonium
84
Astatine
85
Radon
86
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
195.078
196.967
200.59
204.383
207.2
208.980
(209)
(210)
(222)
Ununnilium
110
Unununium
111
Ununbium
112
Ununquadium
114
Uub
Uuq
* Uuh
(289)
(289)
*
Uun
(281)
*
Uuu
(272)
*
*
(285)
Ununhexium
116
Ununoctium
118
*
Uuo
(293)
* Names not officially assigned. Discovery of elements 114, 116, and 118 recently reported. Further information not yet available.
Gadolinium
64
Terbium
65
Dysprosium
66
Holmium
67
Erbium
68
Thulium
69
Ytterbium
70
Lutetium
71
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
157.25
158.925
162.50
164.930
167.259
168.934
173.04
174.967
Curium
96
Berkelium
97
Californium
98
Einsteinium
99
Fermium
100
Mendelevium
101
Nobelium
102
Lawrencium
103
Cm
Bk
Cf
Es
Fm
Md
No
Lr
(247)
(251)
(252)
(257)
(258)
(259)
(262)
(247)
SECTION 3 The Periodic Table
557
The Atom and the Periodic Table
Objects often are sorted or grouped according to the properties they have in common. This also is done in the periodic
table. The vertical columns in the periodic table are called
groups, or families, and are numbered 1 through 18. Elements in
each group have similar properties. For example, in Group 11,
copper, silver, and gold have similar properties. Each is a shiny
metal and a good conductor of electricity and heat. What is
responsible for the similar properties? To answer this question,
look at the structure of the atom.
When a glass rod is rubbed
with silk, the rod becomes
positively charged. Infer
what type of particle in the
atoms in the rod has been
removed. Explain your
answer in your Science
Journal.
Electron Cloud Structure You have learned about the
Figure 10
Energy levels in atoms can be
represented by a flight of stairs.
Each stair step away from the
nucleus represents an increase in
the amount of energy within the
electrons. The higher energy levels contain more electrons.
number and location of protons and neutrons in an atom. But
where are the electrons located? How many are there? In a neutral atom, the number of electrons is equal to the number of
protons. Therefore, a carbon atom, with an atomic number of
six, has six protons and six electrons. These electrons are located
in the electron cloud surrounding the nucleus.
Scientists have found that electrons within the electron
cloud have different amounts of energy. Scientists model the
energy differences of the electrons by placing the electrons in
energy levels, as in Figure 10. Energy levels nearer the nucleus
have lower energy than those levels that are farther away. These
energy levels fill with electrons from inner levels—closer to the
nucleus, to outer levels—farther from the nucleus.
Elements that are in the same group have the same number
of electrons in their outer energy level. It is the number of electrons in the outer energy level that determines the chemical
properties of the element. It is important to understand the link
between the location on the periodic table, chemical properties,
and the structure of the atom.
Step 4 = energy level 4 32 electrons
Step 3 = energy level 3 18 electrons
Step 2 = energy level 2
8 electrons
Step 1 = energy level 1 2 electrons
Floor (nucleus)
Energy
558
CHAPTER 18 Properties of Atoms and the Periodic Table
Energy Levels These energy levels are named using numbers
one to seven. The maximum number of electrons that can be
contained in each of the first four levels is shown in Figure 10.
For example, energy level one can contain a maximum of two
electrons. Energy level two can contain a maximum of eight electrons. Notice that energy levels three and four contain several
electrons. A complete and stable outer energy level will contain
eight electrons. In elements in periods three and higher, additional electrons can be added to inner energy levels although the
outer energy level contains only eight electrons.
Research Visit the
Glencoe Science Web site at
science.glencoe.com for
more information about the
structure of atomic energy
levels. Communicate to your
class what you learned.
Rows on the Table Remember that the atomic number
found on the periodic table is equal to the number of electrons
in an atom. Look at Figure 11. The first row has hydrogen with
one electron and helium with two electrons both in energy level
one. Because energy level one is the outermost level containing
an electron, hydrogen has one outer electron. Helium has two
outer electrons. Recall from Figure 10 that energy level one can
hold only two electrons. Therefore, helium has a full or complete outer energy level. The second row begins with lithium,
which has three electrons—two in energy level one and one in
energy level two. Lithium has one outer electron. Lithium is followed by beryllium with two outer electrons, boron with three,
and so on until you reach neon with eight outer electrons.
Again, looking at Figure 10, energy level two can only hold eight
electrons. Therefore, neon has a complete outer energy level. Do
you notice how the row in the periodic table ends when an outer
energy level is filled? In the third row of elements, the electrons
begin filling energy level three. The row ends with argon, which
has a full outer energy level of eight electrons.
Figure 11
One proton and one electron are
added to each element as you
go across a period in the periodic
table.
Hydrogen
1
Helium
2
He
H
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
3
Li
4
Be
5
B
6
C
7
N
8
O
9
F
10
Ne
Sodium
Magnesium
Aluminum
Silicon
Phosphorus
Sulfur
Chlorine
Argon
11
Na
12
Mg
13
Al
14
Si
15
P
16
S
17
Cl
18
Ar
SECTION 3 The Periodic Table
559
Figure 12
Electron Dot Diagrams Did you notice that hydrogen,
The elements in Group 1 have
one electron in their outer energy
level. This electron dot diagram
represents that one electron.
lithium, and sodium have one electron in their outer energy
level? Elements that are in the same group have the same number of electrons in their outer energy level. These outer electrons are so important in determining the chemical properties
of an element that a special way to represent them has been
developed. An electron dot diagram uses the symbol of the element and dots to represent the electrons in the outer energy
level. Figure 12 shows the electron dot diagram for Group 1
elements. Electron dot diagrams are used also to show how the
electrons in the outer energy level are bonded when elements
combine to form compounds.
H
Li
Na
K
Rb
Cs
Fr
Figure 13
Same Group—Similar Proper ties The elements in
Group 17, the halogens, have electron dot diagrams similar to
chlorine, shown in Figure 13. All halogens have seven electrons
in their outer energy levels. Since all of the members of a group
on the periodic table have the same number of electrons in
their outer energy level, group members will undergo chemical
reactions in similar ways.
A common property of the halogens is the ability to form
compounds readily with elements in Group 1. Group 1 elements
have only one electron in their outer energy level.
Figure 13 shows an example of a compound formed by one
such reaction. The Group 1 element, sodium, reacts easily with
the Group 17 element, chlorine. The result is the compound
sodium chloride, or NaCl—ordinary table salt.
Not all elements will combine readily with other elements.
The elements in Group 18 have complete outer energy levels.
This special configuration makes Group 18 elements relatively
unreactive. You will learn more about why and how bonds form
between elements in the later chapters.
Electron dot diagrams show the
electrons in an element’s outer
energy level.
Cl
The electron dot diagram for
Group 17 consists of three sets of
paired dots and one single dot.
560
Why do elements in a Group undergo similar
chemical reactions?
Na
ⴙ
Cl
ⴚ
Sodium combines with chlorine to give each element a complete outer energy level in the
resulting compound.
CHAPTER 18 Properties of Atoms and the Periodic Table
Ne
Neon, a member of Group 18,
has a full outer energy level. Neon
has eight electrons in its outer
energy level, making it unreactive.
Regions on the Periodic Table
The periodic table has several regions with specific names.
The horizontal rows of elements on the periodic table are called
periods. The elements increase by one proton and one electron
as you go from left to right in a period.
All of the elements in the blue squares in Figure 14 are metals. Iron, zinc, and copper are examples of metals. Most metals
exist as solids at room temperature. They are shiny, can be
drawn into wires, can be pounded into sheets, and are good
conductors of heat and electricity.
Those elements on the right side of the periodic table, in yellow, are classified as nonmetals. Oxygen, bromine, and carbon
are examples of nonmetals. Most nonmetals are gases, are brittle, and are poor conductors of heat and electricity at room temperature. The elements in green are metalloids or semimetals.
They have some properties of both metals and nonmetals.
Boron and silicon are examples of metalloids.
Research Visit the
Glencoe Science Web site at
science.glencoe.com for
more information about
newly discovered elements.
Communicate to your class
what you learn.
What are the properties of the elements located
on the left side of the periodic table?
A Growing Family Scientists around the world are continuing
their research into the synthesis of elements. In 1994, scientists at
the Heavy-Ion Research Laboratory in Darmstadt, Germany,
discovered element 111. As of 1998, only one isotope of element
111 has been found. This isotope had a life span of 0.002 s. In
1996, element 112 was discovered at the same laboratory. As of
1998, only one isotope of element 112 has been found. The
life span of this isotope was 0.00048 s. Both of these elements
are produced in the laboratory by joining smaller atoms into
a single atom. The search for elements with higher atomic numbers continues. Scientists believe they have synthesized elements
114, 116, and 118, too. HowMetalloids
ever, the discovery of these elements has not been confirmed.
Nonmetals
Metals
Figure 14
Metalloids are located along the
green stair-step line. Metals are
located to the left of the metalloids. Nonmetals are located to
the right of the metalloids.
SECTION 3 The Periodic Table
561
Astronomy
Figure 15
Scientists believe that naturally
occurring elements are manufactured within stars.
Elements in
the Universe
Are all of the elements throughout the universe the same? Scientists have made giant strides
in answering this question. Using the technology
that is available today, scientists are finding the
same elements throughout the universe. They
have been able to study only a small portion of
the universe, though, because it is so vast. Many
scientists believe that hydrogen and helium are
the building blocks of the other naturally occurring elements. Atoms join together within stars to
produce elements with atomic numbers greater
than 1 or 2—the atomic numbers of hydrogen
and helium. Exploding stars, or supernovas,
shown in Figure 15, give scientists evidence to support this theory. When stars go supernova a mixture of elements, including
the heavy elements such as iron, are flung into the galaxy. Many
scientists believe that supernovas have spread naturally occurring elements that are found throughout the universe. It is
important to note that all of the superheavy elements—those
with an atomic number above 92—are human-made and found
only in laboratories. Technetium and promethium also do not
occur naturally.
Section
Assessment
1. Use the periodic table to find the name,
atomic number, and average atomic mass
of the following elements: N, Ca, Kr, and W.
2. Give the period and group in which each of
these elements is found: nitrogen, sodium,
iodine, and mercury.
3. Write the names of these elements and
classify each as a metal, a nonmetal, or a
metalloid: K, Si, Ba, and S.
4. Think Critically The Mendeleev and
Moseley periodic charts have gaps for the
as-then-undiscovered elements. Why do
you think the chart used by Moseley was
more accurate at predicting where new
elements would be placed?
562
5. Making and Using Graphs Construct a circle
graph showing the percentage of elements classified as metals, metalloids, and nonmetals. Use
markers or colored pencils to distinguish clearly
between each section on the graph. Record your
calculations in your Science Journal. For more
help, refer to the Science Skill Handbook.
6. Communicating Choose a synthetic element
and write a brief paragraph about it in your Science Journal. Include information about the element’s name, location of the synthesis research,
and the people responsible for its discovery. For
more help, refer to the Science Skill Handbook.
CHAPTER 18 Properties of Atoms and the Periodic Table
A Periodic Table of Foods
U
se your favorite foods to create a periodic
table of foods.
What You’ll Investigate
How can you create a periodic table to organize
your favorite foods?
Materials
11 ⫻ 17 paper
12- or 18-inch ruler
colored pencils or markers
Goals
■ Organize 20 of your favorite foods into a
periodic table of foods.
■ Analyze and evaluate your periodic table for
similar characteristics among groups or
family members on your table.
■ Infer where new foods added to your table
would be placed.
Procedure
1. List 20 of your favorite foods and drinks.
2. Describe basic characteristics of each of your
food and drink items. For example, you
might describe the primary ingredient, nutritional value, taste, and color of each item.
You also could identify the food group of each
item such as fruits/vegetables, grains, dairy
products, meat, and sweets.
3. Create a data table to organize the information that you collect.
4. Using your data table, construct a periodic
table of foods on your 11 ⫻ 17 sheet of
paper. Determine which characteristics you
will use to group your items. Create families
(columns) of food and drink items that share
similar characteristics on your table.
For example, potato chips, pretzels, and cheeseflavored crackers could be combined into a family
of salty tasting foods. Create as many groups as
you need, and you do not need to have the same
number of items in every family.
Conclude and Apply
1. Evaluate the characteristics you used to
make the groups on your periodic table. Do
the characteristics of each group adequately
describe all the family members? Do the
characteristics of each group distinguish its
family members from the family members of
the other groups?
2. Analyze the reasons why some items did not
fit easily into a group.
3. Infer why chemists have not created a periodic table of compounds.
Construct a bulletin board of the periodic
table of foods created by the class. For
more information, refer to the Science
Skill Handbook.
ACTIVITY
563
What’s in a Name?
T
he symbols used for different elements sometimes are easy to figure out. After all,
it makes sense for the symbol for carbon to be C and the symbol for nitrogen to
be N. However, some symbols aren’t as easy to figure out. For example, the element
silver has the symbol Ag. This symbol comes from the Latin word for silver, Argentum.
Recognize the Problem
How are symbols and names chosen for elements?
Form a Hypothesis
How are elements named? Are newly discovered elements named the same way they
were hundreds of years ago? How are the symbols for these elements determined?
Form a hypothesis about why certain elements have their names and symbols.
Goals
■ Research the names and symbols
■
■
■
■
of various elements.
Study the methods that are used to
name elements and how they have
changed through time.
Organize your data by making your
own periodic table.
Study the history of certain elements and their discoveries.
Create a table of your findings
and communicate them to other
students.
Data Source
Go to
the Glencoe Science Web site at
science.glencoe.com for more
information on naming elements,
elements’ symbols, and the discovery
of new elements, and for data from
other students.
564
CHAPTER 18 Properties of Atoms and the Periodic Table
Test Your Hypothesis
Do
Plan
1. Make a list of particular elements
you wish to study.
2. Compare and contrast these elements’ names to their symbols.
3. Research the discovery of these
elements. Do their names match
their symbols? Were they named
after a property of the element,
a person, their place of discovery,
or a system of nomenclature?
What was that system?
1. Make sure your teacher
approves your plan before
you start.
2. Visit the Glencoe Science
Web site for links to different sites about elements, their history, and
how they were named.
3. Research these elements.
4. Carefully record your data in your
Science Journal.
Analyze Your Data
1. Record in your Science Journal how
3. Make a chart of your class’s findings.
the symbols for your elements were
chosen. What were your elements
named after?
2. Make a periodic table that includes
the research information on your
elements that you found.
Sort the chart by year of discovery
for each element.
4. How are the names and symbols for
newly discovered elements chosen?
Make a chart that shows how the
newly discovered elements will
be named.
Draw Conclusions
1. Compare your findings to those of
your classmates. Did anyone’s data
differ for the same element? Were
all the elements in the periodic
table covered?
2. What system is used to name the
newly discovered elements today?
3. Some elements were assigned symbols based on their name in another
language. Do these examples occur
for elements discovered today or
long ago?
Find this Use the Internet
activity on the Glencoe
Science Web site at science.glencoe.com
and post your data in the table provided.
Compare your data to those of other
students. Combine your data with those of
other students to complete your periodic
table with all of the elements.
ACTIVITY
565
SCIENCE AND
HISTORY
SCIENCE
CAN CHANGE
THE COURSE
OF HISTORY!
★
Asia
Europe
North
America
Africa
GREENLAND
A group of people vanish
without a trace. Scientists
turn to ice for the answer.
South
America
★
NORWAY
Austr
ATLANTIC OCEAN
The orange line shows the route the
Norse sailed from Norway to Greenland.
A Chilling
A scientist inspects an
ice core sample from
the Greenland Ice Sheet.
The samples are stored
in a freezer at ⴚ36°C.
566
Drilling to the bottom of the Greenland Ice
Sheet takes place in a deep trench dug in
the snow surface, and uses an electronically controlled drill.
By drilling deep into this ice, scientists can
recover an ice core. The core is made up of
ice formed from snowfalls going way, way
back in time.
By measuring the ratio of oxygen isotopes
in the ice core, scientists can estimate
Greenland’s past air temperatures. The cores
provide a detailed climate history going back
over 80,000 years. Individual ice layers can be
dated much like tree rings to determine their
age, and the air bubbles trapped within each
layer are used to learn about climate variations.
Dust and pollen trapped in the ice also yield
clues to ancient climates.
St ry
Air bubbles and dirt
trapped in ice provide
clues to Earth’s past
climate.
icture this: It’s 1361. A ship from
Norway arrives at a Norwegian settlement in Greenland. The ship’s crew
hopes to trade its cargo with the people living
there. The crew gets off the ship. They look
around. The settlement is deserted. More
than 1,000 people had vanished!
New evidence has shed some light on the
mysterious disappearance of the Norse settlers.
The evidence came from a place on the
Greenland Ice Sheet over 600 km away from
the settlement. This part of Greenland is so
cold that snow never melts. As new snow falls,
the existing snow is buried and turns to ice.
P
A Little Ice Age
Based on their analysis, scientists think the Norse moved to
Greenland during an unusually
warm period. Then in the 1300s,
the climate started to cool and a
period known as the Little Ice Age began.
The ways the Norse hunted and farmed were
inadequate for survival in this long chill.
Since they couldn’t adapt to their colder surroundings, the settlers died out.
Examining ice cores fascinates scientists.
It gives them an idea of what Earth’s climate
was like long ago. The ice cores also may help
scientists better understand why global temperatures have been rising since the end of
the Little Ice Age.
Though life in Greenland ended in a
chilling way for the Norse, that hasn’t been
the story for other people living there. The
native Inuit have flourished by finding ways
to adapt their lifestyles to their environment—no matter what the weather!
CONNECTIONS Research Report Evidence seems to show that
Earth is warming. Rising temperatures could affect our lives. Research
global warming to find out how Earth may change. Report to the class.
For more information, visit
science.glencoe.com
Chapter
18
Study Guide
Section 1 Structure of the Atom
1. A chemical symbol is a shorthand way of
writing the name of an element.
2. An atom consists of a
nucleus made of protons and neutrons
surrounded by an
electron cloud. In the
figure to the right,
how many protons
and neutrons are in
the nucleus?
3. Quarks are particles of matter that make up
protons and neutrons.
4. The model of the atom changes over time.
As new information is discovered, scientists
incorporate it into the model.
Section 3 The Periodic Table
1. In the periodic table, the elements are
arranged by increasing atomic number
resulting in periodic changes in properties.
Knowing that the number of protons,
electrons, and atomic number are equal
gives you partial composition of the atom.
2. In the periodic table, the elements are
arranged in 18 vertical columns, or groups,
and seven horizontal rows, or periods.
3. Metals are found at the left of the periodic
table, nonmetals at the right, and metalloids
along the line that separates the metals from
the nonmetals. In the diagram below, what is
the name of the group of elements that is
highlighted in blue?
Section 2 Masses of Atoms
1. The number of neutrons in an atom can be
computed by subtracting the atomic number from the mass number.
2. The isotopes of an element are atoms of
that same element that have different numbers of neutrons. What is the mass number
of the isotopes below?
4. Elements are placed on the periodic table in
order of increasing atomic number. A new
row on the periodic table begins when the
outer energy level of the element is filled.
3. The average atomic mass of an element is the
weighted-average mass of the mixture of its
isotopes. Isotopes are named by using the
element name, followed by a dash, and its
mass number.
568
CHAPTER STUDY GUIDE
FOLDABLES
After You Read
Without looking at the
chapter or at your Foldable,
write what you learned
about atoms on the Learned fold of your Foldable.
Reading &Study
& Study
Skills
Chapter
18
Study Guide
Complete the following concept map on the parts of the atom.
Atom
contains a
contains an
Electron cloud
contains
contains
contains
Neutrons
also made of
made of
Quarks
Vocabulary Words
Using Vocabulary
a. atom
b. atomic number
c. average atomic mass
d. electron
e. electron cloud
f. electron dot diagram
g. group
h. isotope
i. mass number
j. neutron
k. nucleus
l. period
m. periodic table
n. proton
o. quark
Answer the following questions using
complete sentences.
Study Tip
Don’t memorize definitions. Write complete sentences using new vocabulary words to be certain
you understand what they mean.
1. What is the name of the organized table of
elements that was designed by Mendeleev?
2.What are two elements with the same number of protons but a different number of
neutrons called?
3. What is the weighted-average mass of all
the known isotopes for an element called?
4. What is the name of the positively charged
center of an atom?
5. What are the particles that make up protons
and neutrons?
6. What is the name of a horizontal row in the
periodic table called?
7. What is the sum of the number of protons
and neutrons called?
8. In the current model of the atom, where are
the electrons located?
CHAPTER STUDY GUIDE
569
Chapter
18
Assessment
Choose the word or phrase that best answers
the question.
1. In which state of matter are most of the
elements to the left of the stair-step line in
the periodic table?
A) gas
C) plasma
B) liquid
D) solid
2. Which is a term for a pattern that repeats?
A) isotopic
C) periodic
B) metallic
D) transition
3. Which of the following is an element that
would have similar properties to those
of neon?
A) aluminum
C) arsenic
B) argon
D) silver
4. Which of the following terms describes boron?
A) metal
C) noble gas
B) metalloid
D) nonmetal
5. How many outer level electrons do lithium
and potassium have?
A) 1
C) 3
B) 2
D) 4
6. Which of the following is NOT found in the
nucleus of an atom?
A) proton
C) electron
B) neutron
D) quark
7. The halogens are located in which group?
A) 1
C) 15
B) 11
D) 17
10. The atomic number of Re is 75. The
atomic mass of one of its isotopes is 186.
How many neutrons are in an atom of
this isotope?
A) 75
C) 186
B) 111
D) 261
11. Lead and mercury are two pollutants in the
environment. From information about
them in the periodic table, determine why
they are called heavy metals.
Mercury
80
Hg
200.59
12. Ge and Si are used in making semiconductors. Are these two elements in the same
group or the same period?
13. Using the periodic table, predict how many
outer level electrons will be in elements 114,
116, and 118. Explain your answer.
14. Ca is used by the body to make bones and
teeth. Radioactive Sr is in nuclear waste. Yet
one is safe for people and the other is hazardous. Why is Sr hazardous to people?
8. In which of the following states is
nitrogen found at room temperature?
A) gas
C) metal
B) metalloid
D) liquid
15. Making and Using Tables Use the periodic
table to list a metal, a metalloid, and a nonmetal each with five outer-level electrons.
9. Which of the elements below is a shiny element that conducts electricity and heat?
A) chlorine
C) hydrogen
B) sulfur
D) magnesium
16. Comparing and Contrasting From the
information found in the periodic table and
reference books, compare and contrast the
properties of chlorine and bromine.
570
CHAPTER ASSESSMENT
Chapter
17. Interpreting Data If scientists have determined that a neutral atom of rubidium has
an atomic number of 37 and a mass number of 85, how many protons, neutrons, and
electrons does the atom have?
18. Concept Mapping As a star dies, it becomes
more dense. Its temperature rises to a point
where He nuclei are comHe
bined with other nuclei.
+He
When this happens, the
Be
atomic numbers of the
other nuclei are increased
+He
by 2 because each gains
the two protons contained
+He
in the He nucleus. For
example, Cr fused with
He becomes Fe. Complete
+He
the concept map showing
the first four steps in He
fusion.
19. Interview Research the attempts made by
Johann Döbereiner and John Newlands to
classify the elements. Research the work of
these scientists and write your findings in
the form of an interview.
20. Display Make a display of pictures demonstrating the uses of several elements. List the
name, symbol, atomic number, average
atomic mass, and several other uses for each
element used.
TECHNOLOGY
Go to the Glencoe Science Web site at
science.glencoe.com or use the
Glencoe Science CD-ROM for additional
chapter assessment.
18
Assessment
Test Practice
Larry researched elements that are
nutrients in food. He found that all packaged foods have nutritional labels on
them. This makes it very easy to determine
the nutritional value of the foods you eat.
As he was eating breakfast, he noticed the
label on his cereal that is shown below.
Sweet Wheat Cereal Nutrition Facts
Serving Size
Servings per Container
Amount Per Serving
Calories
Calories from Fat
About 24 biscuits (59g/2.1 oz.)
About 12
Cereal
200
10
Cereal with 1/2 cup
fat free milk
240
10
% Daily Value
Total Fat 1 g
Saturated Fat 0 g
Monounsaturated Fat 0 g
Polyunsaturated Fat 0.5 g
Cholesterol 0 mg
Sodium 5 mg
Potassium 200 mg
Total
Carbohydrate 48 g
Dietary Fiber 6 g
Sugars 12 g
Other Carbohydrate 30 g
Protein 6 g
2%
0%
2%
0%
0%
0%
6%
0%
3%
12%
16%
24%
18%
24%
Study the chart and answer the following questions.
1. According to the chart, which nutrient
below is provided only when the cereal
is eaten with 1/2 cup of milk?
A) saturated fat
C) potassium
B) sodium
D) dietary fiber
2. If Larry were to eat two servings of this
cereal each with 1/2 cup of milk, about
how many grams of dietary fiber
would he eat?
F) 48 g
H) 12 g
G) 24 g
J) 6 g
CHAPTER ASSESSMENT
571